Salicylaldehyde complexes: effects of metal ion substitution, ligand substitution and adduct formation on their infrared spectra

Abstract

The i.r. spectra of forty-two complexes of salicylaldehyde containing the ions Co(II), Ni(II) and Cu(II) are discussed. Metal-oxygen (ν MO), aldehyde carbonyl (νCO) and phenolic carbonyl (νCO) stretching frequencies are assigned by observing the effects of metal ion substitution, substitution in the aryl ring and adduct formation on the spectra. Comparison of the spectra of the anhydrous complexes and their bis(aquo) and bis(pyridine) adducts supports existing evidence for polynuclear octahedral coordination in the anhydrous Co(II) and Ni(II) complexes. Substitution in the aryl ring of the complexes produces shifts in ν MO which are related to the resonance capacities of the substituents. Pyridine adduction causes a depletion of electron density in the CO and M−O bonds which is consistent with its π-electron acceptor properties.